Multiple temperature evaporator



March 1954 w. R. HAINSWORTH 2,670,608

MULTIPLE TEMPERATURE EVAPQRATOR Filed Aug. 16,-1952 INVENTOR.

@ATIORNEY Patented Mar. 2, 1954 MULTIPLE TEMPERATURE EVAPORATOR William. R. Hainsworth, Puente, Calif assignor to Servel, Inc., New York, N. Y., a corporation of Delaware Application August 16, 1952', Serial No. 304,773

The present invention relates to refrigeration and more particularly to refrigeration apparatus for maintaining the desired temperatures in the separate freezing and food storage compartments of a refrigerator cabinet.

Refrigerators usually comprise a high temperature food storage space which should be maintained at a cooling temperature above freezing and a. freezing compartment which should be maintained at a low temperature below freezing- In accordance with a recent trend the low tern-- perature compartment is insulated from the food: storage space to insure a constant low temperature for storing frozen foods over a long period of time. To maintain these separate compartments at different and substantially constant temperatures with the same refrigeration system. presents a difficult. problem because of variations in load conditions.

The varying load; conditions comprise variations in the ambient temperature from day to day, variations: in. the relative amounts of: foods stored in the freezing and food storage comparisments, and variations. in the normal use of, the refrigerator at different periods: during a and the relative use of the two compartments'.v The evaporator may be constructed in separate sec-- tions for the. separate compartments and con nected in series for the continuous flow of re-- frigerant therethrough.

with a refrigeration apparatus is illustrated in,

which refrigerant overflowing from alow ternperature evaporator section enters a drain con.- duit bypassing a high temperature: evaporator section Liquid refrigerant is: fed from a. liquid trap in the drain. conduit. to the topof the: temperature evaporator section: by avapor lift. The vapor liquid-lift. is operated. by a heater controlled by a thermostat responsive to a high temperature condition affected by the high temperature evaporator section todeliver refrigerant to the latter as required.

If the heat transfer surfaces of the different sections are designed for a 6 Claims. (01. 62-5) One of the objects of the present invention is to provide a refrigerator having separate low and high temperature compartments with a 138-.

frigerati'on apparatus having a novel construe-- tion for balancing the load in the separate com partments under all operating conditions.

Another object is to provide a refrigeration apparatus. for normally delivering refrigerant from the outlet of a low temperature evaporator section to the inlet of a high temperature evapo rator section and diverting the refrigerant through a bypass around the high temperature evaporator section upon the occurrence of a low temperature condition. affectedby the latter.

Still another object is to provide a refrigeration apparatus of type indicated with a re frigerant: fee-d conduit between the low and high temperature evaporator sections through which liquid. refrigerant flows by gravity and a heat operated devicev in the feed conduit for producing a vapor lock therein. to divert refrigerant through a drain conduit around the high temperature section.

These and other objects will become more apparent from the foilowing description and drawing in which like referencecharacters denotelike parts. throughout the several views. It is to be expressly understood. however, that the drawing is for the: purpose of illustration only and not a definition of the limits of. invention,v reference being for this: purpose to the appended claims. In the drawing:

The figure is a diagrannnaticv-iew of an absorption refrigeration system incorporatingv the novel features of the? present invention. and showing the heat operated device in the feed. conduitfor controlling the flow of refrigerant to around the high temperature evaporator section.-

For purposes of illustration the present-invention is shown applied to a refrigerator comprising' a cabinet 3 providing a food storage space i adapted to" be" cooled to some temperature above freezing and having a freezing compartment 8' therein insulated from the space t bywallsi 6. It willv be understood that the cabinet 3 may have the food storage compartment 4' completely separated from the freezing compartment 5 with.

separate closures at the outside. of the cabinet. The interior of the refrigerator cabinet 31' ire-- frigeratedby a cooling. element or evaporator I having, a. low temperature" section to to maintain. a substantially constant temperature in the freezing compartment. 5- and: a separate high temperature section: 1 b to maintain a substantially 3 constant temperature above freezing in the food storage space 4.

Evaporator I constitutes one element of a single mechanical refrigeration system and for purposes of illustration is shown applied to a three-fluid absorption refrigeration system generally similar to that illustrated and described in United States Letters Patent to Alvar Lenning 2,300,579, issued November 3, 1942, and entitled Refrigeration. Such a refrigeration system comprises a refrigerant circuit for delivering liquid refrigerant to evaporator f, a gas circuit for delivering an inert gas to the evaporator in which the refrigerant evaporates and diffuses at partial pressure to produce a refrigerating effect, and an absorption solution circuit in which an absorbent is circulated to absorb refrigerant from the gas and from which refrigerant vapor is expelled by the application of heat. The absorption refrigeration system illustrated comprises a generator 8, a condenser 3, the evaporator l, a gas heat exchanger iii, an absorber II and a liquid heat exchanger I2 interconnected for the circulation of refrigerant, absorbent, and the auxiliary pressure equalizing gas.

Generator 8 is in the form of an upright cylindrical vessel having a central or axial flue 3 providing an annular chamber i3 therebetween for absorption solution. Flue i3 is heated by radiant heat and the products of combustion from a fuel burner lb. The top of the annular chamber [4 of generator is connected to the upper end of the condenser 9 by a vapor pipe l5.

Condenser 9 is preferably air cooled and as illustrated comprises a vertically arranged serpentine coil having spaced heat transfer fins [1. The lower or outlet end of condenser 3 is connected to the top of the low temperature evaporator section To by a conduit IS.

The evaporator I is located in the cabinet 3 to be refrigerated and the remainder of the apparatus is generally located at the exterior of the cabinet. Low temperature evaporator section la comprises a'section of pipe bent to generally conform to the shape of the interior of the freezing compartment in which it is located but progressively inclined from the top to the bottom so that liquid refrigerant will flow therethrough by gravity. The high temperature section lb of the evaporator is illustrated in the form of a vertically arranged serpentine coil located in the food storage space 4 and having heat transfer fins 19. The lower end of the low temperature section la is connected to the upper end of the high temperature section lb by a connecting section lc to provide a continuous path for the flow of gas through the evaporator. Liquid refrigerant, however, is drained from the bottom of the low temperature section la and fed to the top of the high temperature section lb by means later to be described in detail. The lower or outlet end of the high temperature evaporator section To is connected by a conduit 20 to one end of chamber 2| of gas heat exchanger ill constituting one path of flow for the inert pressure balancing gas.

The gas heat exchanger I0 is formed by a cylindrical shell 22 having closed ends and spaced tube sheets 23 and 24 therein provide the chamber 2| therebetween. Tubes 25 extend through the chamber 2! between the tube sheets 23 and 24. The space between the tube sheets 23 and 24 and the ends of shell 22 constitute headers 26 and 21 which together with the tubes constitutes a second path of flow for the pressure balancing inert gas in heat exchange with the gas in chamber 2|. A conduit 28 depends from the end of chamber 2| of gas heat exchanger l0 opposite from the end connected to evaporator l and is connected to the lower end 29 of absorber l l.

Absorber H is also illustrated in the form of a vertically arranged serpentine coil and its upper end 30 is connected to header 26 of gas heat exchanger H). The opposite header 2! of gas heat exchanger I0 is connected by a conduit 3| to the top of the low temperature evaporator section la. The lower end of depending conduit 28 extends beyond its connection to the absorber coil and is connected to the top of an absorber pct 33 and the bottom of the absorber pot is connected to the generator 8 by a conduit 34.

Conduit 34 constitutes the inner passage of liquid heat exchanger l2 and a vapor liquid-lift 35. The lift 35 comprisess several turns 35a. of conduit 34 wound around a depending portion [3a of flue l3 and an upright portion 35b having its upper end connected to chamber M of generator 8 adjacent the top thereof. Surrounding the conduit 34 is a sleeve 36 constituting a second passage 31 of liquid heat exchanger l2. A pipe 38 connects the lower end of generator chamber It to one end of the outer sleeve 36 and the opposite end of the sleeve is connected to the upper end or top of the absorber H by a riser 39. As illustrated, riser 39 has a hairpin bend with heat transfer fins 40 thereon.

Heat from fuel burner I5 is transferred through the wall of the flue l3 to the solution in chamber I4 to expel refrigerant vapor therefrom. The refrigerant vapor flows through vapor pipe [6 to condenser 9 where it is condensed to a liquid and the liquid refrigerant flows by gravity through the conduit means 18 to the top of the low temperature evaporator section la. The liquid refrigerant flowing downwardly through evaporator I by gravity evaporates and diffuses into the pressure equalized gas at partial pressure to produce a refrigerating effect and the heavier mixture of refrigerant and gas flows downwardly into the chamber 2! of the gas heat exchanger 10. Gas laden with refrigerant vapor then flows through the chamber 2| in heat exchange relation with the gas weak in refrigerant flowing from the absorber through the tubes 25 of gas heat exchanger l0 and then through conduit 28 into the bottom of the absorber ll. Simultaneously absorption solution weak in refrigerant flows by gravity from the chamber M of generator 8 to the top of absorber H in a path of flow comprising the pipe 38, outer passage 3! of liquid heat exchanger l2 and conduit 39. Absorption solution flowing downward- 1y through the absorber ll absorbs refrigerant vapor from the inert gas in which it is diffused and the lighter gas tends to rise and flow upwardly through the absorber to the header 26 of the gas heat exchanger l0, then through the tubes 25 to the header 2'! and from the header through the conduit 3] to the top of the evaporator 1. Thus, circulation of the pressure equalizing gas is initiated by the differential weights of columns of gas strong in refrigerant and gas weak in refrigerant in the gas circuit.

Absorption solution rich in refrigerant flows from the lower end of absorber H into the absorber pct 33 and from the latter through the conduit 34. The absorption solution in the coils' 35a surrounding the depending extension 13a of flue i3 is heated to expel refrigerant vapor and the expelled vapor lifts the solution through the upright portion 35b of conduit 34 into the top of the chamber 14 of generator 8 for gravity flow through the absorption solution circuit. As thus far described the absorption refrigeration system is substantially identical with that illustrated and described "in the Lenning patent, referred to above, except for the particular construction and arrangement of the separate evaporator sections la and 'lb.

In accordance with the present invention the refrigeration system delivers all of the refrigerant liquefied in the condenser 9 to the top of the low temperature evaporator section la of evaporator '1 for gravity flow therethrough to insure an adequate supply of refrigerant to maintain the desired low temperature in the freezing compartment 5. Surplus refrigerant overflowing from the bottom of the low temperature evaporator section To enters a feed conduit 45 connected to the top or inlet end of the high temperature evaporator section lb for gravity flow therethrough. A heat operated device 46 is provided in the feed conduit 45 for producing a vapor lock therein to stop the flow of refrigerant to the high temperature evaporator section 11) and divert the refrigerant through an overflow drain conduit 4] bypassing the latter section. Operation of the refrigeration system is controlled by a thermostat 4S responsive to a temperature condition affected by the low temperature evaporation section la and operation of the heat operated device 46 is controlled by a second thermostat 49 responsive to a temperature condition affected by the high temperature evaporator section 11) to regulate the supply of liquid refrigerant to each of the separate evaporator sections as required.

The feed conduit 45 comprises a depending pipe 50 having its upper end connected to the lower or outlet end of the low temperature evaporator section In and its opposite end connected to the side of a vessel 5i adjacent the bottom thereof. The vessel may have other shapes but as illustrated is in the form of a bottle having an upper reduced neck portion '52. A 'U-shaped pipe 53 has one end 54 projecting upwardly through the bottom of the vessel 15] to a level above the connection of the pipe 50 therewith, and its opposite end 55 connected to the upper or inlet end cf the high temperature evaporator section It. It will .be noted that the vessel '51 is located below the top or inlet end of the high temperature evaporator section 11) and that the bight portion of the U--shaped pipe 53 depends below the vessel 58. Thus, liquid refrigerant overflowing from the outlet end of the low temperature evaporator section To flows through the pipe 5%] to the vessel 5i and fills the latter and the U-shaped pipe 53 to a level at which the liquid refrigerant will overflow into the high temperatureevaporator section Lb.

The heat operated device 45 for regulating flow through the feed conduit 45 is illustrated in the form of an electric heating element 56 in thermal contact with the reduced neck portion 52 of the vessel 51. The electric heating element 56 is connected to a source of electric current such as an electric power line 51. Electric heating element 56 when energized vaporizes a portion of the refrigerant therein to produce a, vapor lock in the vessel 54 above the upwardly projecting end 54 of the U-shaped pipe 53 to prevent flow of liquid through the latter and cause it to loads up in the depending pipe 50 and overflow through the drain conduit 41 bypassing the high temperature evaporator section 11;.

I'he overflow drain conduit 4! comprises a pipe connected between outlet end of the low temperature evaporator section 1a and the outlet end of the high temperature evaporator section 119 and a branch 41a connected to the pipe 50 above 1b and the 'portion'of conduit i! above the branch constitutes a vent. It will be noted that the depending U-shaped pipe 53 of feed conduit 45 produces a liquid column of a height h to balance the liquid column 71. in the pipe .50, at which level, the refrigerant overflows through the hranchflu.

of bypass drain conduit 41. To prevent the liquid trap in the U-shaped pipe '53 from being blown when the heating element 56 is energized, a vent pipe 58 is connected between the top of the reduced neck portion of vessel 5| to the section 'i-c between the high and low temperature sections. The vent pipe 58 may be of such .di mensions as to restrict the flow of vapor therethrough or may have an orifice therein to limit the vapor flow which will vary in direct proportion to the height of the liquid column h and h.

Thermostat $8 for controlling operation of the refrigeration system may be of any suitable construction for operating a gas valve 59 to regulate the supply of fuel to the burner I5 responsive to a temperature condition affected by the low temperature evaporator section la. As illustrated diagrammatically, the thermostat comprises a bulb 60 so located as to be subjected to the temperature in the freezing compartment 5, a bellows 6| connected to actuate the gas valve v5% and a tube 52 connecting the bulb and bellows. The bulb 5.5, tube 62 and bellows 6| contain a fluid for actuating the bellows upon changes in tem-- perature in the freezing compartment 5 to regulate the amount of gas supplied to burner 15 in accordance with requirements to maintain a substantially constant temperature in the freezing compartment.

The second thermostat 49 controls the heating element 55 of the heat operated device 4'6 and also may be of any suitable construction to energize the heating element in response to a predetermined low temperature condition affected by the high temperature evaporator section lb. The thermostat 49 comprises a bulb 63 so located in cabinet 3 as to be responsive to the food storage space i, a bellows 64 and a tube 6.5 connecting the bulb and bellows. Bellows E4 is connected to actuate an electric switch 65 in one side of the power line 57 connected to the electric heating element 56.. The bulb d3, bellows 64 and tube 65 of thermostat 49 contain a fluid for actuating the switch 68 to closed position at a predetermined low temperature in the food storage space l and open the switch at any temperature above the predetermined low temperature. One form of the invention having now been described in detail, the mode of operation is explained as follows.

For purposes of description let it be assumed that the freezing compartment 5 is above the desired temperature and that thermostat 46 has opened gas valve 5-9 to supply fuel to burner [5. Heat from the gas burner l5 expels refrigerant vapor from absorption solution in the generator 8 and vapor and absorption solution are delivered to the condenser 9 and absorber ll, respectively. Refrigerant liquefied in the condenser l flows through the feed conduit If! to the top of the low temperature evaporator section 1a of the evaporator I and the refrigerant flows by gravity from the top to the bottom of the evaporator section. Simultaneously, inert gas weak in refrigerant flows into the top of the low temperature evaporator section 1a and the liquid refrigerant evaporates and diffuses into the inert gas at a partial pressure and low temperature to produce a refrigerating effect. If the freezing compartment is at a relatively high temperature, the amount of heat transmitted through the walls of the low temperature evaporator section la will vaporize all of the liquid refrigerant as it flows therethrough. As the temperature in the freezing compartment 5 decreases, however, the amount of heat transmitted will decrease and the evap-' orator section is designed to produce and hold the freezing temperature desired when evaporating only a portion of the refrigerant flowing therethrough. Surplus liquid refrigerant at the outlet end of the low temperature evaporator section la flows through the feed conduit 45 comprising the depending pipe 50, vessel 5] and U- shaped pipe 53 into the upper o inlet end of the high temperature evaporator section 112. The refrigerant fills the depending bight portion of the U-shaped pipe 53 and vessel 5! above the outlet end 55 of pipe 53 and below the overflow branch 41a of drain pipe 4?. The liquid refrig erant then flows by gravity through the high temperature evaporator section lb. Simultaneously, gas from the low temperature section Ia flows through the connecting portion l'c of the evaporator to the high temperature section 1b. The liquid refrigerant then evaporates and diffuses into the gas in the manner as previously explained with respect to the low temperature section la but at a higher partial pressure and temperature to produce a refrigeranting effect in the food storage space '3.

When the temperature in the food storage space 4 decreases below a predetermined low temperature, for example 38 F., the thermostat 49 operates to close the electric switch 66 and thereby energize the heating element 56. Heat from the heating element is transmitted through the neck portions 52 of the vessel iii and vaporizes a portion of the liquid refrigerant therein. As the amount of refrigerant vaporized and the pressure of the vapor increases due to the continuous transfer of heat from the heating element 56, the liquid level in the vessel 5| is depressed below the upwardly projecting end 54 of the U-shaped pipe 53 therein and thereby stops the flow of refrigerant to the high temperature evaporator section 11). The vapor pressure in vessel 5| causes the liquid refrigerant to back out through the pipe 50 until it overflows through branch 41a of drain conduit 4'! and bypasses the high temperature evaporator section lb. Simultaneously, the liquid level is depressed in the upright end 54 of the U-shaped conduit 53 to produce a liquid column 71. therein which balances the liquid column 72. in the conduit 50 so that all of the additional refrigerant supplied from the low temperature section la will flow through the overflow drain conduit 4? and bypass the high temperature evaporator section lb. Refrigerant vapor in the reduced neck portion 52 of vessel 5! continuously flows at a predetermined rate through the restricting vent pipe 58 and the rate of flow through the vent varies indirect proportion to the height of the liquidv columns h and h and the capacity of the heating element 56, size of the restricting vent pipe 58 and height of the U-shaped pipe 53 are so designed as to produce an equilibrium condition before the liquid trap blows in the U-shaped pipe 53.

as required to maintain the desired temperature in the food storage space 4. With the arrangement of elements described above, all of the re-- frigerant is available for use when either of the compartments is calling for refrigeration and refrigerant is vaporized to stop the flow of refrigerant to the high temperature compartment onl when the food storage space 4 is below a minimum temperature.

It will now be observed that the present invention provides a refrigeration system having separate freezing and food storage compartments with a refrigeration apparatus for balancing the load in the separate compartments under all opcrating conditions. It will also be observed that the present invention provides an arrangement for feeding liquid refrigerant from the low tem. perature evaporator section directly to the high temperature evaporator section so long as the food storage compartment is above a predetermined low temperature and diverting such re-- frigerant through a bypass around the high temperature evaporator section upon the occurrence: of the predetermined low temperature in the food storage space. It will also be observed that the present invention provides a heat operated.

device in the feed conduit between the low and high temperature evaporator sections which is operative to produce a vapor lock and divert refrigerant through a bypass around the high temperature section.

While a single embodiment of the invention is herein illustrated and described, it will be un--. derstood that modifications may be made in the construction and arrangement of elements without departing from the spirit or scope of the invention. Therefore, without limitation in thisv respect, the invention is defined by the follow-:

ing claims.

I claim:

1. In a refrigerator, a cabinet having separate; compartments. a refrigeration system comprising an evaporator having a low temperature section and a high temperature section in the separate compartments of the cabinet, each of said sections being arranged for the gravity flow of refrigerant therethrough, a refrigerant liquefier inthe system connected to deliver refrigerant to the Y top of the low temperature evaporator section, a feed conduit connecting the bottom of the low temperature section to the top of the high temperature section through which liquid refrigerant fiows by gravity, an overflow drain pipe connected between the feed conduit and the outlet from the high temperature section for bypassing I The apparatus continues to operate with no refrigerant being supplied to the high the latter, the point of connection of said feed conduit with the overflow drain pipe being located above its point of connection with the high temperature section, a heat operated device in the feed conduit for stopping the flow of refrigerant therethrough to cause it to bypass the high temperature evaporator section through the overflow drain pipe, and a control responsive to a temperature condition affected by the high temperature evaporator section for operating the heat operated device.

2. A refrigeration system in accordance with claim 1 in which the heat operated device is a vapor trap in the feed conduit and an electric heating element in thermal contact with the vapor trap for vaporizing refrigerant.

3. A refrigeration system in accordance with claim 1 in which the feed conduit comprises a liquid trap, the heat operated device comprises a vapor trap in the liquid trap and an electric circuit having a heating element in thermal contact with the vapor trap, and the control comprises a thermostatically operated switch in the electric circuit.

4. In a refrigeration system in accordance with claim 1 in which the feed conduit comprises a depending U-shaped liquid trap, the overflow drain pipe, being connected to the feed conduit above the outlet connection of the latter with the top of the high temperature evaporator section,

and the heat operated device comprises a vapor trap in the U-shaped liquid trap and a heating element in thermal contact with the vapor trap.

5. In a refrigeration system in accordance with claim 1 in which the feed conduit comprises a vessel, a depending pipe connecting the outlet end of the low temperature evaporator section to the vessel, a, depending U-shaped pipe connecting the vessel to the top of the high temperature evaporator section, the overflow drain pipe being connected to the depending pipe above the connection of the depending U-shaped pipe with the high temperature evaporator section, said depending U-shaped pipe having a riser of greater height than the height of the feed conduit below the overflow drain pipe, and the heat operated device comprising an electric heating element in thermal contact with the vessel above the connection of either pipe therewith.

6. In a refrigeration system in accordance with claim 1 in which the feed conduit comprises a pipe depending from the outlet end of the low temperature evaporator section, a vessel having an upper restricted neck portion and a depending U-shaped pipe having one end projecting upwardly through the bottom of the vessel above the connection of the depending pipe therewith and its opposite end connected to the top of the high temperature evaporator section, the overflow drain pipe being connected to the depending pipe above the connection of the depending U-shaped pipe with the high temperature evaporator section, a restricting vent pipe connecting the top of the vessel to the high temperature evaporator section, an electric circuit having a heating element surrounding the reduced neck portion of the vessel, and the control comprising a thermostatic switch in the electric circuit.

WILLIAM R. HAINSWORTH.

References Cited in the file of this patent UNITED STATES PATENTS Number 

